First on deck: Three Security Updates for Mac OS X 10.6 Snow Leopard and two flavors of 10.5 Leopard. The updates are aimed at addressing only “a single vulnerability related to handling of embedded fonts by Apple Type Services.” The vulnerability is credited to “cybersecurity researcher” Charlie Miller, who disclosed the findings last month as part of 20 new zero-day holes in Mac OS X.

Two new firmware updates are also available for Apple’s 27-inch iMac model.

The first, 27-inch iMac EFI FW Update 1.0, is a mere 2.1MB download which requires Mac OS X 10.6.3 and is recommended for all quad-core 27-inch iMacs. Among the fixes for the EFI firmware update:

- Resolves an issue that sometimes caused high processor utilization while playing audio through the headphone output mini-jack.

- Resolves an issue that prevented the display backlight from turning on after powering on the iMac.

The second firmware update is labeled 27-inch iMac SMC Firmware Update 1.0 and makes “unspecified compatibility fixes to Target Display Mode.” If you recall, that feature allows the computer to be used as a secondary display via the Mini DisplayPort connector and is exclusive to the 27-inch iMac. The 397KB update requires both Mac OS X 10.6.3 as well as the aforementioned 27-inch iMac EFI Update 1.0.